I'm not going to write a big thing about this, because I didn't do a step-by-step breakdown. Disassembly of this is pretty easy: there's a knurl-head screw on the back at the top of the pocket-clip. If you remove that, the clip comes off and can be set aside. Gently-but-firmly hold the knurled ring at the base of the dome and twist it, and by twisting and pulling, you can extract the top and meter assembly out of the shell.
The front "Brockway Director" label is a card cylinder that can be gently extracted and set aside.
This is as far as I got. Things get hairy after that. I believe that there are hidden screws located under the black Norwood Director face (the part with the f/stop markings). It appears to be glued on, so you would need a razor, scalpel, or some other very sharp knife and a steady hand to remove it. Once that's off, you should be able to take out the screw(s) and lift the top of the dome off, which will expose the selenium cell.